This invention relates to an automatic diluter and more particularly to a diluter which permits aspiration of a very small sample and subsequent dilution of the sample at very high ratios.
Automatic diluters are available which provide for the aspiration of a predetermined quantity of a sample fluid, followed by the discharge of the measured sample together with a predetermined quantity of diluent. While there are many particular constructions of diluters of this class, in each the change of diluent involves the flushing of various hydraulic lines and connections in order to prevent diluent contamination by a previously used diluent. Such diluters typically require a valve assembly for switching purposes between aspirate and dispense modes of operation, the valve assembly being a relatively expensive sub-assembly of the diluter and being a source of possible error.
Another type of apparatus provides a self-contained diluent unit which is removable from the dispenser for subsitution by another diluent unit containing a different type of diluent. A dispensing piston within the diluent unit is driven to dispense diluent through an outlet for diluting a liquid sample which has been measured using other apparatus. The operation of this class of apparatus, therefore, is less useful than an automatic diluter capable of both measuring the sample and dispensing the diluent.
Among the objects of the present invention may be noted the provision of an automatic diluter, and of a diluent module incorporated therein, which facilitates the automatic aspiration of a relatively small sample of liquid and the dilution of that sample with a relatively large volume of diluent, wherein the diluent module is removable from the remainder of the diluter and is interchangeable with other such modules.
Further objects include the provision of an automatic diluter which eliminates hydraulic lines and valving, which permits recovery of unused diluent, and which permits a convenient and precise selection of a wide variety of dilution ratios.